Is it possible to pass passthrough attributes in a custom composite component?

Question

In JSF 2.2, I have a custom composite component which wraps a vanilla component (let's say a h:commandLink).

Is it possible to add passthrough attributes on my composite component and pass them back to the wrapped component?

Something like this (it's an example, don't bother about its uselessness):

Declaration of my:commandLink:

<cc:interface>
    <cc:attribute name="text" type="java.lang.String" />
</cc:interface>

<cc:implementation>
    <h:commandLink a:magicInsertionOfAllThePassThroughAttributes>
        #{cc.attrs.text}
    </h:commandLink>
</cc:implementation>

Use of my:commandLink:

<my:commandLink text="oh no" a:data-something="…" a:data-otherthing="…" />

Styleclass and title are existing attributes on the commandLink. Are you sure you mean 'passThrough' in the JSF 2.2 sense of the word? Or do you just want to be able to have a dynamic number of attributes on your myCommandLink that all automatically mapped to the existing attributes of the h:commandLink? — Kukeltje
My example was pretty bad, I modified it with more exotic attributes. The purpose is indeed to map all unknown attributes for my:commandLink to the wrapped h:commandLink — Xavier Portebois
I've been googling a little and did not find something easy yet (not something complex either). But do you have a 'fixed' list of allowed attributes on the composite or can you define them (would be good for code completion too). If not I think you need to add a Custom component class : docs.oracle.com/javaee/7/tutorial/jsf-custom004.htm#BNAVU. If you can, I think I have a 'solution' — Kukeltje
The purpose here is to handle any passthrough attribute (lots of data- for jQuery behaviors, for example). I didn't find anything useful on google even with a component java class. I'm curious to know what you find :) — Xavier Portebois
Yep... But maybe add checking which ones are the passthough...But explicitly defining the attributes on your component (without the data-prefix) is good too so you can have code completion... in your ide and in the custom component you can add all them via the f:passThroughAttribute tag and add the data- prefix to them. (there is a f:passTroughAttributes too (plural) but I did not find a cc.passThroughAttrs anywhere — Kukeltje

Xavier Portebois Xavier Portebois · Accepted Answer · 2018-03-30T15:22:56

So, following @Kukeltje comments, I managed to do something with a custom composite component backing class:

@FacesComponent("PassThrough")
public class PassThroughComponent extends Component
{
    @Override
    public void encodeBegin(FacesContext facesContext) throws IOException
    {
        super.encodeBegin(facesContext);
        findComponent("pass").getPassThroughAttributes().putAll(getPassThroughAttributes());
    }
}

With a DOM element bearing a id='pass' in my component, I can pass the attributes to it.

Alas, Eclipse doesn't understand the trick, and triggers warnings seeing all these "unknown attribute 'a:something'".

I truly wonder how Primefaces components manage to avoid that.

Is it possible to pass passthrough attributes in a custom composite component?

2 Answers